Conventional adhesives for wind turbine applications include vinyl ester-, epoxy-, and polyurethane-resin based adhesives. These adhesives tend to suffer a variety of limitations that include high internal stresses, bubble formation as a result of air entrapment, requirements of high temperature and lengthy post curing, and poor adhesive bonds in thicker application. Epoxy adhesives in particular have built-in stresses that tend to lead to cracking, yet remain widely used in these applications. Furthermore, epoxy adhesives do not have balanced physical property profiles over wide temperature ranges leading to temperature change induced failure modes.
To-date, DNV GL, the leading certification body for wind turbines has not approved any methyl methacrylate (MMA) based adhesives for wind turbine assembly. Compared to these conventional wind turbine adhesives, MMA has several attractive properties. For example, inherent stresses are high in epoxy-based adhesives, as compared to MMA based structural adhesive. The inherent stress of epoxy-based adhesives is manifest as a cracking phenomenon that is much more pronounced in these systems as compared to MMA under the same operating conditions. Furthermore, epoxy-based adhesives do not have balanced physical property profiles over wide temperature ranges and show poor operating performance in subfreezing temperatures.
Wind turbines are routinely exposed to physically demanding conditions, and are routinely positioned in remote terrestrial and aquatic settings. Due to the limitations of existing adhesives, additional monitoring and service are required to prevent catastrophic failure of the existing adhesives.
Thus, there exists a need for a MMA-based structural adhesive to bond wind turbines and in particular wind turbine blades. There also exists a need for such a formulation that has superior thermal stability to promote formulation storage prior to usage.